Mutation details: This allele, often referred to as wild-type, comprises a novel 131 amino acid protein encoded in a gene comprising four exons, three coding, spanning 18kb. Unique changes in this gene account for all other alleles that have been molecularly characterized. The expression of this allele is almost always dominant to other alleles of this gene.
(J:3523)

The A allele is usually regarded as a wild-type allele. For example,the C3H and CBA mouse sublines are homozygous for agouti. Hairs are black with a subapical yellow band. This black-yellow-black pattern is referred to as agouti. The general appearance is yellowish brown, slightly lighter on the belly than on the back.